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What is a Seyfert Galaxy?

What is a Seyfert Galaxy?

A Seyfert Galaxy is a group of galaxies whose existence was spotted by American astronomer Carl K. Seyfert hence the name. Their existence was noted in 1944. Their luminosity can change over time in matters of days and weeks. It is believed that the 1% of Spiral Galaxies are Seyfert Galaxies. The first Seyfert, BL Lacertae was thought of as a variable star before being identified as a Seyfert Galaxy.Britannica

Seyfert Galaxies fall into two main types, with additional subtypes devised by Daniel Osterbrook in 1981 : Georgia State Uni

Type I - Broad emission lines that is indicative of a concentration of hot gases that are expanding at a rate of over 1000+km/s.

Type I.5 - Narrow permitted components are easily seen.

Type I.8 - Weak Broad Hα and Hβ

Type I.9 - Only weak broad Hα detectable

Type II - These type have strong emission lines but are not as powerful, their speeds are only up to 1000 km/s.

A well known example of a Seyfert Galaxy is NGC 7742 in the constellation of Pegasus. As you can see, this particular one resembles an egg with a central yellow core. It is 74.2 Million Light Years away, a long distance but it is close compared to the nearest quasar which is about 600 million light years away.

The main differences between Quasars and Seyfert Galaxies are :-

Quasars are brighter/luminous than Seyfert Galaxies.

Quasars are further away and are therefore older than Seyfert Galaxies.

Quasars can be detected without observing the galaxies that contain them.

Seyfert Galaxies can be detected by the energetic core and by the radiation from the entire galaxy. Cosmoquest

Related Pages of Interest :-

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